The present invention relates generally to cooling systems. More particularly, the present invention relates to the coolers for regulating the temperature of electronic devices. The present invention is particularly, but not exclusively, useful for cooling systems that regulate the temperature of electronic components of blade servers.
The regulation of the temperature of electronic components like processors due to heat generated inside the housing of an electronic device like a blade server is an important consideration during the design of an electronic device. Cooling is important because if left unchecked, heat can cause electronic devices to malfunction during use or lead to premature device failure. As improvements in processor speed occur, the amount of heat generated by the faster processors also increases. Additionally, improved processors require larger power supplies and auxiliary components that generate increased amounts of heat and require improved systems for heat removal.
Another factor that aggravates the need for improved heat removal cooling systems is the trend towards making computing devices such as blade servers smaller and especially thinner. The trend toward smaller and thinner electronic devices having larger, faster processors renders the traditional heat removal cooling systems inadequate for several reasons. First, smaller devices having faster processors result in an increased density of heat producing by electronic components leading to higher concentrations of heat. Second, a decreased amount of space is available for temperature regulating devices such as traditional heatsinks. Lastly, a decreased amount of space is available to create ventilation paths that pass through the heat-exchanging channels of the heatsink. Thus, traditional cooling systems with blower assembly having one blower with an inlet that ventilates the entire housing of the device and, accordingly, all electronic components are less effective or inapplicable in removing heat when used in smaller, thinner devices.
There are numerous designs of the coolers for direct cooling of electronic components (described, for example, in the patent of Japan No 8-195,456 “Cooler for electronic apparatus”, in the U.S. Pat. No. 5,838,066 “Miniaturized cooling fan type heatsink for semiconductor device”, on the website http://www.dynatron-corp.com/products/cpucooler/1USolution.asp? page=1U, —DC1U-B04) that include the number of cooling assemblies equal to the number of cooling electronic components of the electronic device, so each of said cooler assemblies comprises a heatsink located in the tight contact with the surface of the electronic component and a blower located in the contact with said heatsink. These conventional coolers had been using axial or radial blowers primarily. The radial blower produces an airflow that passes by the heat-exchanging channels and then through the inlet, the impeller and the outlet of said blower to the ambient air.
These cooling systems provide good heat removal. But they are expensive, need a high amount of material, have big overall sizes and not enough high efficiency because of having number of blowers equal to the number of cooling electronic components.
There are numerous designs of the coolers for cooling of electronic components (integrated circuit chips) that include one common heatsink installed in the contact with all or several (at least two) of the electronic components of the electronic device. These coolers have usually one common blower.
The heatsink of such cooler should have tight contact with the surfaces of all said electronic components. But it is difficult to insure that every electronic component will be coupled to the heatsink evenly because of dimensional tolerances from one electronic component (chip) to another. Some of them may not even be coupled at all to the heatsink, while excessive mechanical stress may be imparted to the others.
There have been proposed a number of solutions in the past to these problems. One such solution, described in U.S. Pat. No. 4,235,283 “Multi-stud thermal conduction module” and in IBM Technical Disclosure Bulletin, vol. 24, no. 11A, April 1982, pages 5625, 5626, and in vol. 28, no. 5, October 1985, pages 2237–2238, employs captive pistons or other elements with springs within the heatsink to contact the chips and accommodate variances in the mechanical features and tolerances. This technique is mechanically complex and therefore costly.
Other technique, also described in said IBM Bulletin and in U.S. Pat. No. 5,981,310 “Multi-chip heat-sink cap assembly”, employs the use of thermally conductive material as solder or a thixotropic thermal compound to fill the gaps between the electronic components and the heatsink. This technique is difficult to implement, and it does not gives good enough contact between the heatsinks and electronic components.
It is known solution described in U.S. Pat. No. 5,184,211 “Apparatus for packaging and cooling integrated circuit chips” employs cushions from elastic material between each of the electronic components and the heatsink.
This solution and all other solutions with one common heatsink for several electronic components have one common deficiency—they cannot provide a good tight contact with low thermal resistance (without air bubbles) between the heatsinks and electronic components compared to the heatsinks that are individually installed on each electronic component. So they are not efficient enough. As a result of not enough good contact and of having one common heatsink in the contact with several of the electronic components, these coolers use a lot of energy, has large overall sizes and is expensive because of comprising of big amount of material and parts.
It would be generally desirable to provide a cooler that overcomes this problem and has higher thermal efficiency at smaller sizes.